Chapter 16, Problem 16.1QP

Interpretation Introduction

Interpretation:

A definition for Bronsted acid and base and bronsted definitions differ from Arrheniuss definitions of an acid – base reaction has to be given.

Concept Information:

According to Bronsted- Lowry concepts of acids and bases,

• An acid is $H^{+}$(proton) donor
• A base is a $H^{+}$ (proton) acceptor.

$Conjugateacid =Base+H^{+}$

$Conjugatebase =Acid-H^{+}$

Conjugate acid-base pairs differ by only one proton.

According to Arrhenius concepts of acids and bases,

Acids are substance that produce hydrogen ions or hydronium ions in water. 

Bases are substance that produce hydroxide ions in water. 

Explanation of Solution

Bronsted concepts of acid and base are one of the important concepts used to explain about an acid and a base.

According to the Bronsted concepts, definition for an acid and base can be given as follows,

An acid is a proton donor and base is a proton acceptor.

Consider the reaction of $HCl$ with $H_{2}O$.

${\text{HCl}}_{\left(\text{aq}\right)}\text{+}{\text{H}}_{\text{2}}{\text{O}}_{\left(\text{l}\right)}\to {\text{Cl}}_{\left(\text{aq}\right)}^{\text{-}}\text{+}{\text{H}}_{\text{3}}{\text{O}}_{\left(\text{aq}\right)}^{\text{+}}$

In this reaction,

$HCl$ is the acid and $H_{2}O$ is the base; $HCl$ donates proton and water accepts that proton.

$C{l}^{-}$ is the conjugate base of $HCl$; it is formed after proton donation by hydrochloric acid.

$H_3{O}_{}^{+}$ is the conjugate acid of $H_{2}O$

We are limited to cases in which water is the solvent.  An acid will dissolve in water to produce ${\text{H}}^{\text{+}}\text{ ion}$, while a base will dissolve in water to produce ${\text{OH}}^{\text{-}}$ ions.

Bronsted and Lowry state that an acid is any substance that will donate a proton ${\text{an H}}^{\text{+}}\text{ ion}$.  This includes the case where the donation of the proton is made to a water molecule, but allows for donation of protons to many other substances, opening the door for general acid-base reactions such as

$\text{HCl}\text{+}{\text{NH}}_{\text{3}}\to {\text{NH}}_{\text{4}}^{\text{+}}\text{+}{\text{Cl}}^{\text{-}}$

Bronsted acid and base concepts are based on protons, Arrhenius acid and base concepts are based on both protons and hydroxyl ions.